Metal corrosion is a tremendously costly problem which threatens the functional integrity of environmentally unstable materials. Corrosion in iron and iron mixed with chromium, nickel, etc. to form steels is particularly problematic because of their widespread use and importance in nearly every industry and the consumer market.
For iron and steels, corrosion consists of reactions between oxygen and water with metallic iron to form a host of oxides and hydrates including FeO, Fe.sub.2 O.sub.3, Fe.sub.3 O.sub.4, FeO(OH), Fe(OH).sub.3, and others. These reactions are self-propagating oxidations which begin at the metal surface and proceed inward. The results are pits, spots and hairline patterns seen in the early stages of rusting. These changes in corroded metals result in larger structural problems including loss of strength, ductility, electrical and thermal conductivity, magnetism and visual characteristics such as gloss, color, reflectivity and refractivity.
During tile past decades, approaches to solving problems associated with corrosion included the development of a variety of metal surface treatments that help slow tile initiation and propagation of corrosion and the development of new alloys which are more resistant to oxidation. While, these developments have provided irons and steels with improved corrosion resistance, many of these are too costly to apply to lower-cost materials. Additionally, notwithstanding the advantages associated with these improvements, corrosion of metals, and particularly irons and steels, remains a problem.
Since the corrosion process is self-propagating, effectively removing the corrosion from metal surfaces aids in extending the useful life and improves the appearance of metals which are prone to oxidation. Thus, processes for efficiently removing the products of corrosion after they have formed are possible alternatives to using much more costly alloys and surface treatment processes. Unfortunately, the oxides and hydrates of iron are soluble in neither aqueous-based systems nor organicbased systems, complicating the problems associated with developing rust removal systems.
A number of rest removing products have been made available for consumer and industrial use. Most of these, however, require long-term exposure to the corroded metal at elevated temperatures or multiple applications over periods of hours. Moreover, typically these preparations are environmentally unsafe and are too toxic for consumer use. Additionally, the consistency of the products and their ability to adhere or wet to metal surfaces is poor. Moreover, when allowed to remain in contact with the atmosphere for very long time periods, the film formers in many of these products forms an adhesive bond with the rust or the base metal. These films are frequently very difficult to remove.
Accordingly, it is an objective of the present invention to provide a composition having superior rust removing characteristics and which is relatively non-toxic and environmentally safe.
It is additionally an objective of the present invention to provide a composition for removing rust from oxidized metals by simple coating or immersing techniques.
It is furthermore an objective of the present: invention to provide a composition which will remove rust without the need for multiple applications and elevated temperatures.
It is also an objective of the present invention to provide compositions which will lift rust from the corroded surfaces and then easily rinse from metal surfaces along with the rest.